Help needed on a big tank project, low tech

[ceg4048]

Vermiculite is a type of clay. If it's clay, then it has a good enough CEC to be useful. Not all CEC is created equally though and I think that may be why Vermiculite is not as popular as it once was. But so what? All that means is that someone was more of a dreamer and then woke up and got real. It depends on the cations that are attracted to the surface. In Vermiculite's case it tends to attract Calcium more so than Potassium as opposed to something like Muscovite, which has a higher selectivity for K+. According to AquaBotanic, Vermiculite is OK at attracting PO4 but not NO3 directly. It can pull NH4 but does not make it easily available to plants, so this then requires bacterial activity to convert the NH4 to NO3. No big deal. You may need to top this with basic gravel as well to keep it from sending particles everywhere, especially if you have digging fish. It does float as well so requires soaking for a week or more.

I thought the Diatomite is that material they use in Diatom filters. It is very fine, almost like talcum powder so that might not be the best. How ironic that this is just the dried silica shells of the very same diatomic algae that everyone moans about...

From what I gather, Kanuma is basically pumice. They just dig it out of the ground in that region of Japan. I'm personally not overly impressed with the CEC of pumice (this is what ADA Powersand is). It might be great for Bonzai but I reckon you can do better. The nutrient retention in pumice has more to do with it's porosity, not much with chemical attraction of nutrient ions although it does have some CEC.

Cheers,

 

[dw1305]

Hi all,
I think Clive s' post pretty well covers it , I've just read that diatomaceous earth does have quite a large CEC c. 50 meq/100g, (from this useful pdf. http://files.clino.webnode.com/200000022-0bdf60cd97/What is CEC.pdf).

If you use peat I wouldn't use a large amount, and over time the CEC of the substrate will decline as the peat is oxidised, other than that it works.

The advantage of a clay mineral is that it will last indefinitely. Can you get calcined clay (or "Fullers Earth") based cat litter? Another possibility would be bentonite based "drilling mud" (they also use it for sealing land-fills etc.).

cheers Darrel

 

[tel]

Thanks, Clive, Darrel,
Locally, inexpensive (being the key word) options are starting to run a little thin, due to the quantities needed mail order is not going to happen as the rates make it too expensive.

I did have a look at bentonite, I think it is used in cat litter. Again, though there are different types of bentonite, calcium, potassium, sodium. I think predominately the cat litter is Calcium Bentonite.
Fullers earth is not available here Darrel, from what I have been research so far.

The Vermiculite seemed a good option as it was local. I am still looking into bonsai retailers for options and also gardening centers to see what I can come up with. I did find out that a lot of wineries use laterite, I just need to find out where they are getting it from

cheers tel

 

[tel]

Just in case you may be wondering why my posting seems a little nonsensical / or incomplete, most times is that it is being done at about half six - seven in the morning before I rush out the door for work.

Back to the vermiculite, Clive I kind of get what you wrote with the regards to the cation attraction. I do get a little lost with the converting NH4 to NO3. Even though it does not readily attract NO3 directly, I would have thought plants would draw this from water column directly ( if you take my meaning). What I am wondering though is becasue it does not attract directly, and requires the biological conversion, does that mean greater levels of toxicity for fish using Vermiculite.

Also, again things that run through my head, as these substrates absorb nutrients from the water column, would it not mean that the PPM levels would fluctuate until the substrate is full (for want of a better term). The thinking then being that you would have high levels of nutrients going until thre substrate is fully absorbed, then scale back


cheers tel

 

[ceg4048]

Hi tel,
Don't worry too much about the NH4 to NO3 issue. First of all because, you are right about the water column uptake. Since all this happens in the sediment the toxicity isn't an issue unless you constantly uproot and dig into the sediment, which you shouldn't be doing very often anyway. Sometimes, a lot of gunk and detritus builds up after time and you want to get rid of it. Since you 're not changing the water in a low tech, just wait every six months or so and do a water change while vacuuming out the gunk. Thirdly, you cannot help but build up bacteria in the sediment particles so that after some weeks the bacteria on the surface of the vermiculite will convert NH4 anyway, so this is absolutely nothing to worry about.

You would really have to do very careful tests to actually see much of a difference in some of this stuff we're talking about. As you've figured out, it's only if the tank were on the edge of starvation that these issues would be worrisome, and of course you're not going to let that happen because you will dose the water column occasionally. The biggest issue is all about the ergonomics of the sediment; does it cloud the water, does it require soaking to make it sink, is it messy, do I need to top it, does it look pretty, is it expensive and so forth. 8)

Cheers,

 

[dw1305]

Hi all,
Laterite doesn't have much CEC, but I can't remember the actual value, and calcium bentonite would be better than sodium (I think it is the sodium form that expands, but I'd need to check). I'm bit short of time but I'll have a look later.
cheers Darrel